A triangle has vertices at coordinates (2,2), (5,6) and (6,2).  What is the number of units in the length of the longest side of the triangle?
Answer: We must find the distance between each pair of points.

The distance between $(2, 2)$ and $(6, 2)$ is 4, since these two points have the same $y$-coordinate.

The distance between $(2, 2)$ and $(5, 6)$ is $\sqrt{(5 - 2)^2 + (6 - 2)^2} = \sqrt{9 + 16} = 5$.

The distance between $(5, 6)$ and $(6, 2)$ is $\sqrt{(6 - 5)^2 + (2 - 6)^2} = \sqrt{1 + 16} = \sqrt{17}$.

Out of 4, 5, and $\sqrt{17}$, 5 is the largest value. Thus, the longest side of the triangle has length $\boxed{5}$.